A cylindrical pipe with a radius of 12.5 cm is filled with water to a depth, `d` cm, as shown.
The surface of the water has a width of 20 cm.
What is the depth of water in the pipe?
- 2.5 cm
- 5.0 cm
- 7.5 cm
- 12.5 cm
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A cylindrical pipe with a radius of 12.5 cm is filled with water to a depth, `d` cm, as shown.
The surface of the water has a width of 20 cm.
What is the depth of water in the pipe?
`B`
`text{Triangle base}\ = 20/2=10\ text{cm}`
`text{Let}\ x =\ text{⊥ distance from centre to water}`
`text{Using Pythagoras:}`
| `12.5^2` | `=x^2+10^2` |
| `x^2` | `=12.5^2-10^2=56.25` |
| `x` | `=\sqrt{56.25}=7.5\ text{cm}` |
`d=12.5-7.5=5.0\ text{cm}`
`=>B`
Two right-angled triangles, `ABC` and `ADC`, are shown.
Calculate the size of angle `theta`, correct to the nearest minute. (3 marks)
--- 6 WORK AREA LINES (style=lined) ---
`41°4^{′}\ \ text{(nearest minute)}`
`text(Using Pythagoras in)\ DeltaACD:`
| `AC^2` | `= 2.5^2 + 6^2` |
| `= 42.25` | |
| `:.AC` | `= 6.5\ text(cm)` |
`text(In)\ DeltaABC:`
| `costheta` | `= 4.9/6.5` |
| `theta` | `= cos^(−1)\ 4.9/6.5` |
| `= 41.075…` | |
| `= 41°4^{′}31^{″}` | |
| `= 41°5^{′}\ \ text{(nearest minute)}` |
The diagram shows a block of land `ABCD` that has been surveyed. All measurements are in metres.
Calculate the length of `AB`, correct to the nearest metre. (2 marks)
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`46\ text{m}`
Daniel conducts an offset survey to sketch a diagram, `ABCD`, of a block of land.
Daniel walks from `A` to `C`, a distance of 62 m.
When he is 15 m from `A`, he notes that point `D` is 25 m to his right.
When he is 57 m from `A`, he notes that point `B` is 20 m to his left.
This is his notebook entry.
--- 6 WORK AREA LINES (style=lined) ---
--- 4 WORK AREA LINES (style=lined) ---
| a. | ![]() |
b. `text(Using Pythagoras:)`
| `CD^2` | `= 47^2 + 25^2` |
| `= 2834` | |
| `:. CD` | `= 53.235…` |
| `= 53\ text{m (nearest m)}` |
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--- 4 WORK AREA LINES (style=lined) ---
a. `text(Proof)`
b. `67°23^{′}`
a. `ΔABC\ text(is right-angled if)\ \ a^2 + b^2 = c^2`
| `a^2 + b^2` | `= 5^2 + 12^2` |
| `= 169` | |
| `= 13^2` | |
| `= c^2\ …\ text(as required.)` |
b. `sin ∠ABC = 12/13`
| `:.∠ABC` | `= 67.38\ …°` |
| `=67°22^{′}48^{″}` | |
| `= 67°23^{′}\ \ \ text{(nearest minute)}` |
Two trees on level ground, 12 metres apart, are joined by a cable. It is attached 2 metres above the ground to one tree and 11 metres above the ground to the other.
What is the length of the cable between the two trees, correct to the nearest metre?
`C`
`text(Using Pythagoras)`
| `c^2` | `=12^2+9^2=144+81=225` |
| `c` | `=\sqrt{225}=15,\ \ c>0` |
`=>C`